CALIFORNIA MICRO DEVICES

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12/5/2000

9

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CMPWR160

Typical Thermal Characteristics

Thermal dissipation of junction heat consists primarily of

two paths in series. The first path is the junction to the

case (

θ

package style, and the second path is the case to

ambient (

θ

board layout.

The overall junction to ambient (

θ

equal to:

θ

For a given package style and board layout, the operat-

ing junction temperature is a function of junction power

dissipation P

in the following thermal equation:

T

= T

The CMPWR160SA is housed in a thermally enhanced

package where all the GND pins (5 through 8) are

integral to the leadframe (fused leadframe). When the

device is mounted on a double sided printed circuit

board with two square inches of copper allocated for

“heat spreading”, the resulting

θ

Based on a maximum power dissipation of

1.0W (2Vx500mA) with an ambient of 70°C the resulting

junction temperature will be:

T

= 70°C + 1.0W (50°C/W)

= 70°C + 50°C = 120°C

All thermal characteristics of the CMPWR160SA were

measured using a double sided board with two square

inches of copper area connected to the GND pins for

“heat spreading”.

Measurements showing performance up to junction

temperature of 125°C were performed under light load

conditions (5mA). This allows the ambient temperature to

be representative of the internal junction temperature.

Note: The use of multi-layer board construction with

power planes will further enhance the thermal perfor-

mance of the package. In the event of no copper area

being dedicated for heat spreading, a multi-layer board

construction, using only the minimum size pad layout,

will typically provide the CMPWR160SA with an overall

θ

dissipated.

Output Voltage vs.Temperature

Figure 14 shows the regulator V

the maximum rated junction temperature. A 125°C

variation in junction temperature from –25°C causes an

output voltage variation of about 50mV, reflecting

a voltage temperature coefficient of approximately

±50ppm/°C.

Figure 14. V

3.35

3.25

3.27

3.29

3.31

3.33

–25

25

075

Temperature (˚C)

50

100

125